1a. Objectives (from AD-416):
Develop an efficient high-throughput genotyping test for accurately determining which ovine TMEM154 protein variants are encoded on an animal’s genomic DNA. This information predicts the relative susceptibility of sheep to ovine lentivirus infection. These infections are the cause of ovine progressive pneumonia (OPP) in the U.S. and visna/maedi around the world. The purpose of this assay development is to provide a commercially available test for sheep producers and researchers to use. Results describing the assay design features, performance, and interpretation will be submitted to a suitable journal for peer review.

1b. Approach (from AD-416):
Assay for six single-nucleotide polymorphisms (SNPs) and two deletions will be designed from ovine DNA sequence information derived from more than 6,000 sheep of multiple breeds. These assays will be developed for a matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS) platform and/or other platforms like qPCR, depending on unique attributes of the ovine TMEM154 gene sequence. The accuracy and robust nature of the assays will be evaluated on control DNA samples that have been previously sequenced to determine their genotype.

3. Progress Report:
Development of a genetic test for susceptibility to ovine progressive pneumonia virus. Visna/Maedi is a debilitating viral disease that affects sheep in many parts of the world. In North America, it is known as ovine progressive pneumonia where it causes respiratory distress and chronic wasting. Previous research by ARS researchers at Clay Center, Nebraska showed that sheep with one variant form of the transmembrane protein 154 gene (TMEM154) were significantly less likely to become infected compared to those with the ancestral form of the same gene. In collaboration with a commercial partner, a genetic test was developed to predict an animal’s susceptibility to infection by detecting mutations in this gene. When combined with removing infected animals, selectively breeding sheep that are less susceptible to infection is expected to help eliminate the disease and prevent flocks from reinfection.
The first commercial use of the test began in April of 2012. Last year, the company tested approximately 2,000 samples of which 1,611 were for our research purposes. This year, the company tested approximately 3,000 samples of which approximately 1,250 were for research purposes.